Hollow charge for land mines



April 8, 1969 R. FRANZEN E L HOLLQW CHARGE FOR LAND MINES Filed April 10, 1967 .lllii'llillillilli'llll Ill INVENTGP Pale/1d FP/WZE/Y Paul Sl/VDEPfll/MW United States Patent Office 3,437,036 HOLLOW CHARGE FOR LAND MINES Roland Franzen and Paul Sindermann, Nuremberg, Germany, assignors to Diehl, Nuremberg, Germany Filed Apr. 10, 1967, Ser. No. 629,714 Claims priority, application Germany, Apr. 20, 1966, D 49,898 Int. Cl. F42b 23/06 US. Cl. 102-8 12 Claims ABSTRACT OF THE DISCLOSURE The present invention concerns a hollow charge for land mines with an upwardlly directed effect for fighting movable targets with limited bottom armament in which the ratio of the wall thickness of the elfective explosive layer on the inside of the housing of the mine to the wall thickness of a conical insert extending into the explosive layer is at least over the major portion of the conical wall surface of said insert approximately constant.

The present invention concerns land mines with upwardly directed hollow charge effect for destroying movable targets with limited bottom armament.

Mines are well known which consist of a relatively large explosive charge and are placed into the roads or the terrain and which solely on the basis of their bursting and splintering effect damage movable targets from below or from the side, in which instances the damage to the armament of the armored vehicles was only sufficient to immobilize the vehicle. In addition thereto also mines are known which are adapted by means of a hollow charge to pierce the armament. Besides hollow charge magnetic mines which are manually attached to a vehicle, there has also become known a land mine with an upwardly directed hollow charge which from a certain depth attacks the vehicle moving thereover while the cover layer above the hollow charge is blown off for instance by a propellant charge prior to detonating the hollow charge, i.e. prior to the hollow charge becoming elfective.

With a hollow charge mine of the above mentioned type, a considerable quantity of explosive is necessary in order to obtain the desired effect. Therefore, the mine is not only heavy and expensive but also requires a covered placing which in turn requires considerable digging work and is relatively diflicult to camouflage.

It is, therefore, an object of the present invention to provide a hollow charge for a lighter land mine which with vehicles having a relatively limited bottom armament will be able not only to produce a hole in said armament but will also impart energy to a pushrod representing a hollow charge insert, which energy will behind the armament give the pushrod over a relatively large distance a bursting as well as a burning effect.

It is another object of this invention to provide a hollow charge as set forth in the preceding paragraph, which is relatively small and can easily be camouflaged with a minimum of digging work.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawing diagrammatically showing a longitudinal section through the charge built-up of -a rotation symmetric hollow charge according to the present invention.

3,437,036 Patented Apr. 8, 1969 The objects set forth above are in conformity with the present invention realized by a suitable selection of the ratio of the effective explosive layer of the hollow charge with regard to the wall thickness of the conical hollow charge insert, and furthermore by a suitable outer conical angle of the insert. The said ratio of the wall thickness of the effective explosive cover of the hollow charge with regard to the wall thickness of the conical hollow charge insert is to be so selected that it is at least over the major portion of the conical mantle surface of the hollow charge insert approximately constant. Assuming a density of the explosive of 0' (g./cm. and a density of the material of the insert of a (g./cm. the ratio of the cover to the insert wall thickness may amount to approximately 3 x (1 /0 When employing a material for the insert, as for instance a zinc kneading alloy, with a density of 5.0 (g./cm. and an explosive with a density of approximately 1.7 (g./cm a ratio will be obtained of thickness of explosive cover:insert wall thicknessz9.

When the charge is cylindrical within the range of the hollow charge insert, it has proved advantageous so to design the hollow charge insert that it increases primarily linearly in thickness from the marginal portion toward the center. The mentioned ratio of the explosive cover to the insert wall thickness is most effective when the explosive cover in the remaining portion of the charge is approximately semispherical.

Referring now to the drawing in detail, it will be noted that in a housing wall 1, which in downward direction has an approximately semispherical to parabolic shape, an explosive filling 3 is provided between a conical hollow charge insert 2 and the mantle or wall 1. The hollow charge insert 2 which consists of a material generally employed for hollow charge inserts, as for instance copper, a zinc alloy, or the like, increases linearly in wall thickness from the marginal area toward the center. On the basis of the above mentioned relationship and assuming that an insert material is employed which has a density of 5 gr./cm. and that an explosive is employed with a density of 1.7 (gr./cm. for instance hexotol 60/40, an optimum relationship of explosive to wall thickness over the respective conical zone of the insert 2 to the wall thickness of the hollow charge insert 2 resulted in this range of approximately 9:1. With other insert materials or changed explosive, naturally other relationships will be obtained.

The opening angle of the hollow charge insert 2 is approximately The conical angle toward the explosive cover 3 is accordingly smaller, for instance 82. The rear tip 4 of the insert 2 may be cut olf and replaced by a cone of inert material, as for instance polyethylene. The hollow charge insert 2 is centrically journalled in the housing wall 1 by means of a ring 5 and is connected to the housing wall 1. A wall 6 arranged adjacent to the explosive filling 3 and forming a part of ring 5 while serving as base compacting means extends approximately at a right angle with regard to the outer wall of the insert cone 2. Ring 5 may consist for instance of aluminum.

The lower portion of the housing wall 1 ends in a threaded neck 7 in which a transfer charge 8 is located which precedes the explosive filling. This transfer charge *8 consists for instance of a pressed tablet of nitropenta. A bell-shaped screw connection 9 of neck 7 is provided with a centric focusing device 10 for the ignition jet. The central axis of said focusing device is located in the axis of symmetry of the hollow charge 2, 3 or transfer charge 9. In front of the focusing device 10 there is provided an electric detonator cap 11.

The design of the hollow charge 3 as mentioned above and of its insert 2 brings about that during the ignition a considerable portion of the insert 2 is deformed to a particularly energy-rich pushrod. The insert now becomes a relatively short thick hollow charge jet. This hollow charge jet produces a hole in the armament and permits the pushrod without material loss in energy" to pass behind the armament, namely into the interior of the vehicle. A hollow charge jet designed in this way also retains its effectiveness over different distances.

In order to realize a great destructive effect in the interior of the armored vehicle, a high pushrod efficiency is aimed at. This will be realized on one hand by the explosive charge cover in relationship to the hollow charge insert, and on the other hand by the opening angle. The limitation in this connection is the angle at which no longer a jet is produced but at which the deformed insert will fly off as an entirety. As has been already mentioned, with the suggested insert material and the employed explosive, an optimum cover ratio is obtained at 1:9.

Tests with the described mine construction have shown that for instance with a charge caliber of 56 mm. and a blasting distance of the size of five times the diameter of insert 2, i.e. 22.0 mm., with a steel armor plate of 20 mm., a projectile inlet diameter of 9 mm., a projectile outlet diameter of 9 mm., and a chip plate of 20 mm. were obtained. A Dural plate placed at a distance of 800 mm. and having a thickness of 2 mm. showed a piercing opening of 100 x 80 mm. A second 2 mm. Dural plate placed at a further distance of 1600 mm. showed still perforations of a diameter of from 3 to 5 mm. in a field of 200 x 150 mm.

If the distance from the hollow charge is increased from five times the insert diameter to seven times the insert diameter, i.e. to 308 mm., the 20' mm. steel armor plate showed a shooting-in diameter of 8 mmand a shooting-out diameter of 10 mm. but no chipping. The first 2 mm. Dural plate at a distance of 800 mm. behind the armored plate shows a perforation diameter of 100 mm. The second 2 mm. Dural plate located 1600 mm. behind the first plate shows perforations with a diameter of from 3 to 5 mm. in a field of 220 x 120 mm.

If under the last mentioned test conditions ammunition is introduced into the center between the 20 mm. armored plate and the first Dural plate, said ammunition is instantaneously burned off or brought to a detonation depending on whether the projectiles or the propellant charge sleeves are hit by the jet. In both instances, in addition thereto also the Dural plate placed therebehind was pierced by portions of the pushrod as well as by splinters of the hit ammunition.

According to a further test, instead of introducing ammunition between the 20 mm. armored plate and the first Dural plate, there was used cleaning cotton permeated with diesel oil. During the firing an open fire resulted and also the above mentioned piercing efficiency in the second Dural plate.

The above described comparison of the fight distances of 220 mm. and 308- mm. shows that the differences in effectiveness are immaterial. A sufliciently large hole is always produced in a customary bottom armament. In addition thereto, in the interior of the vehicle there is obtained a blasting and burning effect as well as a certain piercing effect which is also able to pierce ammunition containers, canister walls, and the like, and to expose the material stored therein so as to bring the same to a detonation. The hit vehicle will therefore become not only immobilized but will also become completely fight unworthy. The operating personnel will be forced to leave the vehicle, and in most instances the vehicle will burn out.

The above described explosive covering of for instance nine times the insert wall thickness represents the optimum in effectiveness at a minimum of hollow charge dimensions and consumption of explosives in case the materials listed by way of example are employed as explosive for the insert. An extension of the explosive container toward the rear or downwardly, for instance in the form of a cylinder, does not bring about any material changes of the hollow charge effect, i.e. of the blasting and burning effect of the pushrod.

A hollow charge built up in the above mentioned manner is suitable for an installation in a corresponding mine system.

What we claim is:

1. A hollow charge for land mines with an upwardly directed effect for fighting movable targets with limited bottom armament, which includes: housing means, an explosive layer arranged within said housing means and having its outer side confined by said housing means, and a conical hollow charge insert confining said explosive layer at the inner side thereof, the wall thickness of said hollow charge insert increasing from its marginal area toward its central portion primarily in a linear manner, the ratio of the wall thickness of the effective explosive layer to the wall thickness of the conical insert with both thicknesses measured along lines at least approximately perpendicular to the inner surface of said insert being approximately constant over at least the major range of the conical wall surface of said hollow charge insert.

2. A hollow charge according to claim '1, in which the explosive layer has a density of 0' and in which the conical insert has a density of 1 the ratio of the thickness of the explosive layer to the Wall thickness of said insert equalling approximately three times 0 /0 3. A hollow charge according to claim '1, in which the density of the explosive is 1.7 grams per cubic centimeter while the density of said insert is 5.0 grams per cubic centimeter, and in which the ratio of the thickness of said explosive layer to the thickness of said insert is approximately 9:1.

4. A hollow charge according to claim 1, in which the ratio of the wall thickness of the effective explosive layer to the wall thickness of the hollow charge insert with both thicknesses measured along lines at least approximately perpendicular to the inner surface of said insert is approximately 9:1.

'5. A hollow charge according to claim 4, in which the opening angle of the hollow charge insert amounts to approximately 6. A hollow charge according to claim 1, in which the tip of the conical insert is fiat.

7. A hollow charge according to claim 6, in which the flattened tip has arranged adjacent thereto a cone of inert material.

8. A hollow charge according to claim 7, in which said inert material is polyethylene.

9. A hollow charge according to claim 1, in which said housing means has the lower portion thereof follow a semispherical contour with the center thereof located approximately at the tip of said conical insert.

10. A hollow charge according to claim 1, in which said housing means has the lower portion thereof follow a parabolic contour with the focus thereof located approximately at the tip of said conical insert.

11. A hollow charge according to claim 1, in which the lower end of said housing means is provided with a cylindrical threaded connection, and which comprises threaded cap means threadedly engaging said cylindrical threaded connection and defining therewith a chamber, a transfer charge located in said chamber, and fuse means connected to said cap means, said cap means being provided with a conical passage for focusing the fuse jet to said transfer charge.

12. A hollow charge according to claim 1, which includes ring means inserted into the upper portion of said housing means and engaging the upper marginal portion of said insert while centering the latter, said ring means 6 11/1965 Paul et a1. 102'24 2/1967 Venghiattis 10224 2/1967 Thomanek 10'2-8 X FOREIGN PATENTS 8/1966 Switzerland.

VERLIN R. PENDEGRASS, Primary Examiner.

US. Cl. X.R. 

